Marine Electrical Systems USCG Question #1226 (Set 41)

How is the main shaft rotation on an AC diesel-electric propulsion vessel normally reversed?

Official USCG Answer & Rule Citation

Correct Answer: Option C — reversing any two phase leads to the motor

Reversing an AC induction or synchronous motor is achieved by swapping any two of the three-phase power leads. This action reverses the phase sequence of the rotating magnetic field within the stator, causing the motor to develop torque in the opposite direction, thereby reversing the shaft rotation.

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